Feeding ring for feeding ore into furnaces

ABSTRACT

A feeding device for feeding materials into the batching silos of a light arc furnace or similar, said device having a ring shaped shelf for receiving the material, a stationary ring shaped roof above the shelf provided with an opening for feeding the material onto the shelf, at least one stationary side wall constituting together with the roof and the shelf a circular space surrounding the material supported on the shelf, essentially gas- and dust-tight seals between the shelf and the stationary parts related thereto and scrapers operable to be brought near the shelf surface to force the material carried thereon to fall down over the shelf edge into the receiving silos.

United States Patent Tuovinen et a1.

FEEDING RING FOR FEEDING ORE INTO FURNACES Inventors: Frans Heikki Tuovinen; Seppo Ilmari Blomquist; Risto Markus Heikkilfi, all of Tornio; Jorma Bruno Honkasalo, Westend; Kalevi Johan Kunttu, Matinkyla, all of Finland Assignee: Outokumpu 0y, Helsinki, Finland Filed: Feb. 20, 1974 Appl. No.: 443,977

Foreign Application Priority Data Feb. 26, 1973 Finland 572/73 [56] References Cited UNITED STATES PATENTS 1,208,248 12/1916 Wedge 214/21 2,297,289 9/1942 Collis et a1... 214/21 2,480,726 8/1949 Greyson 214/18 R 11/1952 Willey 222/408 X 2,699,249 l/l955 Milliken, Jr. et al 198/188 X 2,804,309 8/1957 Sweet 222/408 X 2,889,786 6/1959 Maffei et a1. 214/18 FOREIGN PATENTS OR APPLICATIONS 102,994 9/1963 Norway 222/408 Primary ExaminerRobert B. Reeves Assistant Examiner-David A. Scherbel Attorney, Agent, or Firm-Brooks Haidt I-Iaffner & Delahunty [5 7] ABSTRACT A feeding device for feeding materials into the batching silos of a light are furnace or similar, said device having a ring shaped shelf for receiving the material, a stationary ring shaped roof above the shelf provided with an opening for feeding the material onto the shelf, at least one stationary side wall constituting together with the roof and the shelf a circular space surrounding the material supported on the shelf, essentially gasand dust-tight seals between the shelf and the stationary parts related thereto and scrapers operable to be brought near the shelf surface to force the material carried thereon to fall down over the shelf edge into the receiving silos.

7 Claims, 12 Drawing Figures PATENTED AUB] 91975 Fig.1

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FEEDING RING FOR FEEDING ORE INTO FURNACES BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for controlled feeding of materials into the batching silos of a light arc furnace or the like. The material may e.g., be in the form of pellets of different size and composition fed into a melting furnace.

2. Description of the Prior Art In various smelting furnaces for ore concentrates or metal components, it is usually important that the material can be fed into the furnace evenly and without variations in the composition of the feed. For example, in a light arc furnace in which the heating takes place by means of electrodes which have one end immersed in the furnace, the prerequisite for good smelting results in that the various components of the batch can be fed evenly as a homogeneous mixture around each electrode so that the conductivity of the batch is the same between each electrode and that the gases generated in the smelting zone flow evenly through the feeding batch.

It must be also remembered that the specific weights of the various components of the feed mixture may vary within a rather extensive range (e.g., about 1-4 g/cm) as may the particle size (e.g., diameter about 3-25 mm), which tends to complicate feed control.

It is previously known to feed a preheated material into, for example, light are furnace batching silos along several slightly slanting pipes above the silos. It has, however, been noted that a preheated feed cools relatively much in these pipes. In addition to cooling, the different components of the feed mixture are classified, in which case the feed arriving in the light arc furnace is no longer homogeneous and its conductivity varies periodically and between the different electrodes. This results in an uneven electric load and a decrease in the smelting efficiency, in some cases there is even a release of the electric voltage. Furthermore, in any case an appropriate distribution of the feed must be obtained between the various pipes, and then the problem of providing an even batching is accompanied by the difficulty of constructing a system so dustand gas-tight that its environment meets the requirements set for working surroundings. Since in a light arc furnace the electrodes are vertical and they are lengthened at the upper end when the lower end melts away, the said previously known distribution-pipe system may, owing to its space requirement and placement, complicate the continual work of renewing the electrodes.

From, for example, British Pat. No. 1,272,379 a rotating circular grating is known which is used for heating metallic machining chips which contain combustible impurities such as oil, in order to form briquets, in which case the said impurities are removed by burning. In this solution, the material shelf is, however, bowllike and provided with fixed scrapers, and the device is therefore not suitable for the purpose meant in the present invention. A homogeneous feed mixture flow cannot be divided into several separate homogeneous partial flows with the said bowl-like device.

SUMMARY OF THE INVENTION According to the present invention there is provided a feeding device which comprises a ring shaped horizontal material shelf supported rotatably about its vertical axis and positioned above batching silos, a ring shaped roof mounted stationary above a material shelf and provided with at least one opening for pouring the material onto the shelf, at least one stationary ring shaped wall joining the roof and closely related to the material shelf, substantially gas-tight and dust-tight tightening means between the material shelf and stationary parts related thereto, and at least two working scrapers supported movably adjacent the shelf to be brought periodically near the shelf surface thereby deflecting material on the shelf over the shelf edge down into the batching silos.

It is an object of the present invention to provide a feeding and distribution device with which an even batching with a homogeneous composition is obtained in the batching silos, a device which does not complicate the operation of lengthening the electrodes and prevents the gases and dust from escaping into the working environment.

In addition to the foregoing the following advantages are gained with the feeding ring according to the present invention: a continuous and even feeding of the material is obtained and the material can be also fed to the feeding ring at several points. The feeding ring can be made gasand dust-tight and can be linked to the other process apparatuses in a gasand dust-tight manner. The feeding rate of the feeding ring can be controlled within a wide range. The feeding ring is suitable for feeding both hot and cold material. The cooling of a heated feed in the feeding ring is less than 5 For example, compared with a telfer conveyor previously used, the operation and maintenance costs of the feeding ring are considerably less.

An increase of about 20 in the annual production of ferrochromium has been achieved with a feeding ring according to the invention, the manufacturing expenses simultaneously decreasing by about 9 BRIEF DESCRIPTION OF THE DRAWINGS FIG. 3 shows a cross section, at point AA in FIG.

2, of a covered feeding ring,

FIG. 4 shows a cross section, at point BB in FIG. 2, of a covered feeding ring,

FIG. 5 shows a cross section, as in FIG. 3, of another embodiment of the invention,

FIG. 6 shows a cross section, as in FIG. 4, of the embodiment according to FIG. 5,

FIGS. 7 and 8 show one embodiment of the feeding ring scrapers as seen from the side and from above,

FIGS. 9 and 10 show another embodiment of the feeding ring scrapers as seen from the side and from above, and

FIGS. 11 and 12 show different embodiments of the feeding ring supporting rollers.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Deviating from conventional solutions in which a hot feed is lifted from the furnace, the cylindrical furnaces l and 2 have been placed above the batching silos 4 of the light are furnace 3 and a feeding ring 5 according 3 to the invention has been placed between the cylindrical furnace 2 and the batching silos 4. By placing the cylindrical furnaces and 2 above the batching silos 4 of the light are furnace 3, the lifting ofa hot feed is eliminated. The bulk of a cold feed, whichis considerably easierto convey upwards, is fed into the cylindrical furnace l and part of the feed directly into the furnace 2. The feed is heated in the cylindrical furnaces, and

simultaneously it flows through the process always by gravity, downwards. The cylindrical furnace 2 discharges the heated feed into the feeding ring, from where it is fed further into the batching silos 4 of the light are furnace 3.

The material shelf 6 is a steel-structured, circular ring (FIGS. 2 and 3 One side of the shelf 6 'has been provided with a rim 7 which prevents the feed from flowing to the wrong side. The material shelf 6 has been lined with fire-resistant lining 8 because of the hot feed 9. The lining material is concave at the bottom of the feeding ring 5. The so-called cold feed 10 remaining in the concavity protects the bottom lining of the material shelf from wear and tear and from an excessive heat load. The feeding ring rotates continuously in one direction, but when so desired it may also be constructed to rotate in both directions or reciprocally. The material shelf 6 can also be without the side rim 7, in which case the discharging of the feed can be carried out, when sodesired, from either side or from both sides, as shown in FIGS. 5 and 6. When a cold feed is used, no fire-resistant lining is necessary. The bottom of the material shelf can also be straight.

The feeding ring has been enclosed in a' closed circular space consisting of a roof 11, a side part 12, a feeding ring material shelf 6, and a rim 7. The spaces be tween the feeding ring and the roof 11 and the side part 12 are sealed by circulating cool water. The water circulates in troughs l3 and 14 attached to the edge of the feeding ring and to the side part 12. The sealing plates 15 and-l6 which have been directed downwards and attached gas-tightly to the inner edge of the roof and the lower edge of the material shelf are constantly partly immersed in the water in the troughs. The water flows first into the upper trough 13, from where it flows as an overflow into the lower trough l4 and from there away as an overflow carrying with it part of the impurities from the troughs. The sealing water can be replaced with other suitable harmless liquids or applicable pulverous materials. The sealling can also be carried out with slide seals in which the seals consist of slide surfaces which are situated opposite each other or tangent to each other and are made from a suitable material.

Therole of the scrapers 17 shown in FIGS. 2, 4, and 6 is to remove the feed mixture from the feeding ring at the desired point and at the desired moment. The scrapers 17 work in a vertical direction. Their driving devices are hydraulic cylinders which raise and lower the scrapers 17 at the desired moment. The driving devices of v the scrapers 17 are automatically or manually controlled. The scraping of the feed mixture from 'the feeding ring takes place when the scraper is in the lower, or scraping, position. A scraper consists of a fireand wear-resistant blade 18 which can be changed, a scraper body 19 with arms 20 and securing members 21, and a water-cooled scraper box 22 with its guide surfaces. The box 22 of a scraper 17 also serves as a supporting and guiding structure of the scraper and scraper 17 is in the upper position, the water-cooled scraper box 22 rapidly conducts heat away from the scraper, thereby promoting the cooling of the scraper,

and prevents heat radiation from the feed mixture and the gas 2 atmosphere from affecting the scraper 17. When a cold feed mixture is used, a water-cooled scraper box is not necessary. If the feed mixture is dustless, the scraper box need not necessarily be tight. In the embodiment shown in FIG. 6 the scraper 17 consists of two parts. The parts are at an angle in relation to each other so that they form a plough and push the feed over both edges of the material shelf.

The scraper 17 can also be structurally and operationally a plate-like blade which pushes from the side, a jointed knife working from the side in a vertical direction, a propeller rotating about its horizontal axis and provided with one or more blades, or a platelike blade which turns around its vertical or horizontal axis. In the embodiment shown in FIGS. 7 and 8, the scraper 17 consists of a screw feeder 23 which can be moved in a vertical direction. The scraper shown in FIGS. 9 and 10 is a propeller 24 which rotates about its vertical axis and is provided with one or more blades.

The material shelf 6 rests through rails 25 attached to its bottom on roller pairs 26 blades at regular intervals. The roller pairs'26 can be changed even during the operation owing to their easy and simple securing manner. The supporting roller system 26 can also be attached to the material shelf as shown in FIG. 11. The supporting roller systems can also be replaced with rings of rollers or balls 27 (with one or several rows of them). One such embodiment is shown in FIG. 12.

The driving machinery of the feeding ring consists of a direct-current motor 28, a gear 29, and a spike wheel 30, which transmits the power from the driving machinery through a toothed wheel 31 to the feeding ring material shelf 6, thereby rotating the latter. The rotating velocity of the driving machinery and thereby that of the material shelf can thus be controlled. To achieve smooth operation of the material shelf, an even number of driving machines is always used. The driving device can also be, as in the embodiment according to FIG, 5, a hydraulic motor 32, coupled to the shaft 33 of the material shelf supporting wheel either directly or through gears. The power to the material shelf 6 can be also transmitted by chain transmission or friction transmission.

During the operation the material shelf is kept on its 2 correct path by a number of supporting wheels 34 or centering members, spaced evenly at the inner circumference of the material shelf, provided with adjustable spring-loaded lever arms supported from the floor. Spring loading can be replaced with torsion bar springs of rubber or with hydraulic or pneumatic cylinders. The power transmission devices of the operating machines can serve as centering members, or the supporting wheels 26, supporting rollers 27, or the respective device of the material shelf 6 can be constructed so that they also serve as the centering device of the material shelf. If the situation allows, the material shelf can be attached with bearings at its center point of rotation, in which case separate centering members are not necessary.

What is claimed is:

l. A device for feeding and distributing a heated material, especially a charge of preheated ore concentrates into the batching silos of a light are furnace, which comprises a ring shaped horizontal material shelf supported rotatably about its vertical axis and positioned above said batching silos,

a ring shaped roof mounted stationary above the material shelf and provided with at least one opening for pouring the heated material onto the shelf,

at least one stationary ring shaped wall joining the roof and closely related to the material shelf,

substantially gas-tight and dust-tight tightening means between the material shelf and stationary parts related thereto,

at least two working scrapers supported movably adjacent the shelf to be brought periodically near the shelf surface thereby deflecting material on the shelf over the shelf edge down into the batching silos, and a water cooled scraper box for each scraper into which the scraper is withdrawn periodically between periods of material deflecting operation.

2. A device according to claim 1, wherein the material shelf, the roof and at least one stationary wall constitute an essentially ring-shaped gas-tight and dusttight space surrounding the material supported on the shelf.

3. A device according to claim 1, wherein the material shelf is rotatable in both directions.

4. A device according to claim 1, wherein the rotation speed of the material shelf is adjustable.

5. A device according to claim 1, wherein the tightening means comprises at least two continuous circular trough fixed to the stationary parts and filled with a sealing material, and corresponding circular sealing plate members fixed to the rotating material shelf and partially immersed into the sealing material.

6. A device according to claim 5, wherein the continuous troughs are filled with a liquid and have an overflow to keep the liquid level constant in the trough.

7. A device according to claim 5, wherein the two troughs are positioned at different heights and the liquid flowing from the upper trough is directed as an overflow into the lower trough. 

1. A device for feeding and distributing a heated material, especially a charge of preheated ore concentrates into the batching silos of a light arc furnace, which comprises a ring shaped horizontal material shelf supported rotatably about its vertical axis and positioned above said batching silos, a ring shaped roof mounted stationary above the material shelf and provided with at least one opening for pouring the heated material onto the shelf, at least one stationary ring shaped wall joining the roof and closely related to the material shelf, substantially gas-tight and dust-tight tightening means between the material shelf and stationary parts related thereto, at least two working scrapers supported movably adjacent the shelf to be brought periodically near the shelf surface thereby deflecting material on the shelf over the shelf edge down into the batching silos, and a water cooled scraper box for each scraper into which the scrAper is withdrawn periodically between periods of material deflecting operation.
 2. A device according to claim 1, wherein the material shelf, the roof and at least one stationary wall constitute an essentially ring-shaped gas-tight and dust-tight space surrounding the material supported on the shelf.
 3. A device according to claim 1, wherein the material shelf is rotatable in both directions.
 4. A device according to claim 1, wherein the rotation speed of the material shelf is adjustable.
 5. A device according to claim 1, wherein the tightening means comprises at least two continuous circular trough fixed to the stationary parts and filled with a sealing material, and corresponding circular sealing plate members fixed to the rotating material shelf and partially immersed into the sealing material.
 6. A device according to claim 5, wherein the continuous troughs are filled with a liquid and have an overflow to keep the liquid level constant in the trough.
 7. A device according to claim 5, wherein the two troughs are positioned at different heights and the liquid flowing from the upper trough is directed as an overflow into the lower trough. 